The invention relates to a syringe with a cylinder and a plunger arranged within the cylinder. Provision is made for a sealing element, which rests against an inner wall of the cylinder with a contact region and seals an annular gap between the plunger and an inner wall of the cylinder. The contact region has a front section, which, in the rest state, rests against the inner wall of the cylinder with contact pressure. The plunger is connected to the sealing element such that the sealing element does not follow an initial movement of the plunger from the rest state and that the sealing element follows a continued movement of the plunger.
Such syringes serve to eject a liquid or pasty substance in a targeted and metered fashion. By way of example, these syringes are used in medical and dental applications. The substance is contained in an interior of the syringe. As a result of pressure on the plunger said plunger penetrates further into the cylinder, and so the space available to the substance reduces. The substance emerges from the cylinder and is emitted—for example through a hollow needle—at the desired spot.
The sealing element is used to seal the interior of the cylinder such that the substance is prevented from emerging between the plunger and the inner wall of the cylinder. In order to have a sufficient sealing effect, the sealing element rests against the inner wall of the cylinder with contact pressure. When the syringe is in the rest state, the result of the contact pressure is static friction between the sealing element and the inner wall of the cylinder. It is well known that the static friction between two surfaces at rest relative to one another is greater than the dynamic friction between two surfaces that move relative to one another. When the syringe is operated, it is initially necessary to overcome the static friction in order to set the sealing element in motion relative to the cylinder. Thus, there is a relatively high initial resistance before the sealing element moves. High initial resistance when operating the syringe is first of all not very user friendly. Secondly, sudden breaking free of the plunger can lead to the contents of the syringe emerging in an uncontrolled manner.